The search for the molecule or molecules responsible for the formation, proliferation, differentiation and maintenance of tissue and organs, such as the pancreas, has been extensive. The structures of several proteins in the family designated as Hepatocyte Nuclear Factors-3/Forkhead or HFH, have previously been elucidated. Weigel et al., Cell, 57: 645-658 (1989); Weigel and Jackle, Cell, 63: 455-456 (1990). The HNF3 branch of the HFH family, HNF3.alpha., -3.alpha., and -3.gamma., were originally identified in hepatocytes, and were hypothesized to be liver transcription factors which bind to recognition sites in DNA regulatory regions. Costa, in Liver Gene Expression, (Tronche and Yaniv, eds.) at pp. 183-204 (R. G. Landes Company)(1994). It was further observed that binding of different combinations of liver factors provided varied promoter control while minimizing the requisite number of regulatory proteins. Thus, the HNF3 family may be capable of regulating the transcription of multiple proteins. During gastrulation of mouse embryos, murine HNF3.beta. and -3.alpha. were observed to be expressed during early and late primitive streak stages of gastrulation, respectively. Later in development, all three known HNF3 genes (HNF3.alpha., -3.beta., and -3.gamma.) were expressed in the gut, pancreas and liver primordium, while only HNF3.alpha., and -3.beta. were expressed in lung. All three HNF3 genes were co-expressed in parenchymal hepatocyte cells, and in HepG2, H4IIE and FTO-2B hepatoma cell lines. HNF3.alpha. and -3.beta. were found to be expressed in the lung and in lower amounts in the intestine, whereas HNF3.gamma. MRNA is transcribed in the testis but not in sertoli cells. HNF3.beta. protein is also expressed in the pancreas, where it recognizes a HNF3 binding site required for transcriptional activation by the .alpha.-amylase enhancer region. The HNF3.alpha. gene is abundantly transcribed within a thin epithelial cell layer lining the pulmonary bronchioles, suggesting that it may regulate the transcription of genes whose protein products are secreted into the lung airway. HNF3.beta. is absent from the bronchiolar epithelium, but expressed at high levels in the smooth muscle surrounding bronchioles and arterioles, suggesting that the HNF3 genes may regulate different target genes. The HNF3 proteins have been shown to collaborate with other liver transcription factors to regulate the expression of over a dozen liver genes, including serum carrier proteins, pharmacologically active polypeptides and genes encoding enzymes involved in glucose metabolism. Thus, the HNF3 proteins are capable of regulating a large number of genes with differing effects. Lai et al., PNAS USA 90: 10421-10423 (1993) found that HNF3.alpha. and HNF3.beta. showed an inhibitory effect in cells of pancreatic origin on the promoter of the glucagon gene. Thus, the HNF3 proteins are capable of regulating genes present in pancreatic cells.